Individual differences in sensitivity and responsiveness are striking characteristics of the chemosensory modality of olfaction. Specific anosmia describes a selective deficit to a specific class of closely related chemical compounds among individuals with otherwise normal olfactory acuity. Specific anosmia has proven to be a promising tool for the study of the genetic basis of olfactory function, as well as the interplay of genetics with environmental and developmental influences. In spite of a growing literature on this potentially important chemosensory phenomenon, few if any studies have examined the responses of specific anosmics to stimuli above threshold or in physically complex mixtures. Such extension of psychophysical findings is necessary if the phenomenon of specific anosmia is to be shown to have relevance to real-life olfactory functioning of humans since most odor-guided behaviors involve stimulation above threshold or with chemical mixtures. Many compounds which are known to show strong individual differences in olfactory sensitivity (and thus are either candidates for or already-documented cases of specific anosmia may influence food flavor perception and thus food choice and food rejection and ultimately play a part in the interaction of the chemical senses with nutritional status and the quality of life. The proposed research will explore the psychophysical responses of individuals with specific anosmia to a number of important aroma and flavor components of foods, with respect to odor intensity and quality perceptions in mixtures. Methods will include psychophysical scaling of perceived intensity in perceptually separable odor mixtures and multidimensional scaling of odor similarities among more blended (i.e. less perceptually divisible) stimuli. Special emphasis will be placed on examining judgements of intensity of other mixture components in addition to those to which the person is anosmic, since second order effects such as mixture inhibition among odor components may also change when one or more mixture components are reduced in their sensory impact. The proposed research will provide a quantitative assessment of these changes in controlled psychophysical studies, as a first step toward bridging the gap between threshold studies of specific anosmia and everyday perception of odors and volatile flavors.